A simple model is presented for calculating the forces between closed-shell atoms and molecules in the regions both of the attractive well and of the repulsive wall at shorter distances. Account is taken of both the overlap of the separate atomic densities and of electron correlation. Applications to pairs of rare gas atoms and to alkali halide molecules demonstrate quantitative agreement with empirically determined intermolecular potentials for these systems over the whole range of separations inside and including the potential minimum.

We test the applicability to atoms of the uniform electron gas energy expression in terms of the local atomic electron density. By using the known atomic electron densities obtained from an independent method (Hartree-Fock) for the density in the electron gas energy expression, we calculate some atomic energies, one-electron energies, and atomic ionization potentials and compare the results with the Hartree-Fock energy values. We calculate the local kinetic energy and exchange energy densities in Hartree-Fock atoms, and compare these results with the corresponding electron gas energy densities. We suggest a simple correction to the electron gas energy to be used for systems not paired in spin, and test this correction. We examine the effect of the finiteness of the atoms by treating a uniform electron gas with a finite number of electrons.

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Interaction potentials for alkali ion-rare gas and halogen ion-rare gas systems J. Chem. Phys. 88, 6290 (1988); 10.1063/1.454467 Comment on ''Recent determinations of potassium ion-rare gas potentials'' Potential energy curves from the electron gas model. II. The ion-rare gas interactionsInteractions of the rare gas atoms with some alkali and halide ions are treated using the model presented in our previous paper [J. Chern. Phys. 56, 3122 (1972)]. In the calculation of the interactions of an atom and an ion. the electron density of the combined system is assumed to be equal to the sum of the two separate electron densities. The Coulombic energy contribution to the interaction energy is calculated directly from the charge distribution of the nuclei and the assumed electron density. The non-Coulombic part of the interaction energy is calculated from the electron density by integrating the uniform electron gas energy expression over the local electron density. The calculated potential curves agree very well with available experimental results over the entire repulsive wall. At larger distances, the model fails. because in its present form it does not include induction forces.The total interaction energy between these two systems is then separated into two parts, the Coulombic and the non-Coulombic parts. The non-Coulombic part of the interaction energy is evaluated using the electron gas energy expression in terms of the local denSity:

The ion-pair interaction potentials obtained by using the model presented in our previous paper are applied to some ionic crystals. The calculated lattice properties of alkali-halide and alkaline-earth-dihalide crystals agree quite well with experimental data. The polymorphic transitions of alkali-hahde crystals at high pressures are also successfully described by the calculations.